An electrochemical measuring cell of the kind referred to above is described in published German patent application DE-OS No. 3,609,402. In this known measuring cell, the gas molecules to be detected penetrate through the pores of the measuring electrode up to a gel-like electrolyte and effect an electrochemical reaction at the three-phase boundary defined by the electrode-gelelectrolyte-gas. The electron transfer connected therewith effects a current flow which is a measure of the concentration of the gas to be detected. For this amperometric operating sensor, the characteristics are substantially determined by the geometry of the sensor head in addition to the pure material characteristics of the membrane, electrode and electrolyte. The detection component (or measurement species) does not completely react in the pore channels for the short pore length to cross section ratios. The detection component can dissolve in the electrolyte chamber and trigger drift effects and/or memory effects via back-diffusion. Furthermore, the unfavorable ratio between the active measuring surface and the electrolyte-covered electrode surface leads to an unnecessarily high residual current. The large pores lying far apart from each other lead to a small effective measuring surface from which a low surface-related sensor sensitivity results. A relatively thick foil is used as a diffusion membrane in the sensor referred to above and this leads to high response times and a reduced measuring sensitivity.